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Initially, dye tracing was strictly a qualitative science. Dye was injected into
a location and then people would sit and wait for it to come out of some other
location.
Later it was discovered that some of these fluorescent dyes would absorb onto
charcoal grains. The dye could then be removed from the charcoal grains with
an alcohol-based solvent. This major discovery allowed for mesh packets containing
charcoal to be placed in springs and streams and left unattended while the dye cloud
passed by. No longer was it necessary to have people sitting at numerous locations
waiting for dye to suddenly appear. The number of possible resurgence points was
no longer an issue. There was still one problem that both of these techniques had
in common. Both relied upon the human eye and subjective opinion for determining
whether dye was present. This was usually not a problem for strong concentrations
of dye, but when the samples or locations had low to mid-range concentrations it was
often difficult to find a consensus among the viewers. This problem was addressed
with the introduction of a device called a filter fluorometer. |
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